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Panel on Genetically Modified Organisms

Health risk assessment of the adjuvant effects of Cry proteins from genetically modified plants used in food and fodder
Health risk assessment of the adjuvant effects of Cry proteins from genetically modified plants used in food and fodder
Photo: iStockphoto
The Norwegian Scientific Committee for Food Safety (VKM) finds it unlikely that Cry proteins in processed genetically modified (GM) maize and soya pose an increased health risk compared with food based on isogenic non-modified plants.

This is concluded from VKM's health risk assessment of food and feed based on GM plants that have one or more cry genes inserted from Bacillius thuringiensis (Bt) to make them resistant to insect attack.

Cry proteins (Bt toxins) are also ingredients of certain biological pesticides used in both organic and conventional farming in many countries. Pesticides containing Bt toxins are not permitted in Norway.

VKM has assessed whether Cry proteins may act as immunological adjuvants, and thereby promote immune responses to other components (e.g. allergens) in food. The potential consequence is food allergy, which could be very serious to the persons affected.

Sources of human exposure are naturally occurring Bt in soil residues on foods, GM plants - mainly maize and soya; inhalation from pesticides; and residues of Bt toxins on plants, such as tomatoes. The concentration of Cry proteins in GM plants is much higher than in conventional food, even higher than in plants that have been sprayed with Bt pesticides for insect control.

Low risk to humans and animals

On the basis of present knowledge, VKM finds it very unlikely that Cry proteins in food increase the health risk to humans. The amount of Cry proteins that would be ingested from GM food is low, due to denaturation and degradation of Cry proteins during heat treatment and other types of processing prior to marketing.

For animals, VKM finds it reasonable to assume that a possible adjuvant effect is unlikely to affect the animal´s health. It is also very unlikely that consumption of food from animals that have eaten feed containing Cry proteins will exert adverse effects on human health.

VKM has found no published evidence of adverse effects of Cry proteins in dust from GM material by inhalation or by the skin exposure, nor of any Cry-mediated adjuvant effect exerted by these routes.

Knowledge gaps

VKM emphasizes that there are many knowledge gaps related to assessment of Cry proteins as potential adjuvants.

More than 500 cry gene sequences have been identified to date, which encode Cry proteins classified into 67 different groups. Only two of the ten Cry proteins that are currently used in GM plants, Cry1Ab and Cry1Ac, have been tested experimentally regarding adjuvant effects. Studies have shown that Cry1Ac applied systemically or mucosally may induce immunological reactions and allergic symptoms in the mouse, for instance by eliciting an IgG response to a co-administered antigen.

The possibility that Cry1Ac could cause such “by-stander” sensitization on mucosal contact by reducing the epithelial barrier function should be explored. It is also uncertain whether this potential adverse effect likewise applies to Cry1Ab.

Altogether, uncertainty remains whether natural adjuvants and Cry protein may cause allergies in a real life situation. It is known that the quantities of Cry proteins in GM maize and soya are low compared to the amounts of other adjuvants in non-modified foods, such as mushrooms, onions, beans and peanuts.

This risk assessment has been performed by VKM's Panel on genetically modified organisms at the commission of the Norwegian Food Safety Authority.

This assessment was published 21 November 2012

Risk assessment closed: 21.11.2012

Contact details

Norwegian Scientific Committee for Food Safety
Phone +47 21 62 28 00
E-mail vkm@vkm.no